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Brightest Cluster Galaxies and Intracluster Light - Observations Magda Arnaboldi European Southern Observatory (Garching) O

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Brightest Cluster Galaxies and Intracluster Light - Observations Magda Arnaboldi European Southern Observatory (Garching) O Brightest cluster galaxies and intracluster light - Observations Magda Arnaboldi European Southern Observatory (Garching) O. Gerhard, L. Coccato, G. Ventimiglia, S. Okamura P. Das, M. Doherty, K. Freeman, E. Mc Neil, N. Yasuda, J.A.L. Aguerri, R. Ciardullo, K. Dolag, J.J. Feldmeier, G.H. Jacoby. M. Arnaboldi – BCGs and ICL: observations ESO, FVC+, 27 June - 01 July 2011 1 Outline 1. Brightest Cluster Galaxies and Intracluster light in clusters 2. Planetary nebulae as kinematical tracers 3. The Virgo cluster & M87 – The PNs’ VLOS and the projected phase space distribution – Dynamical status of the Virgo core – Large scale distribution of the ICL 4. The Hydra cluster & NGC 3311 – Observations : long-slit spectroscopy, MSIS, surface photometry – Debris from disrupted galaxies by the cluster potential 5. The Coma cluster core & the NGC 4874/NGC 4889 binary merger 6. Conclusions M. Arnaboldi – BCGs and ICL: observations ESO, FVC+, 27 June - 01 July 2011 2 1. ICL from deep photometry • Core of the Coma cluster: Photographic photometry Thuan & Kormendy 1977 • Abell 4010 (left, z=0.096) Abell 3888 (center, z=0.151) Deep CCD photometry Krick & Bernstein 2007 Abell 1914 (right) Feldmeier+2004 See also Melnick+’77, Bernstein ’95, Feldmeier+’04, Gonzalez+’05, Mihos+’05, Krick+’06 See contributions from J. Krick, J. Melnick, C. Rudick, S. Okamura M. Arnaboldi – BCGs and ICL: observations ESO, FVC+, 27 June - 01 July 2011 3 ICL properties in individual clusters • ICL surface brightness profile shape varies between clusters - Krick & Bernstein 2007 • Ellipticity generally increases with radius, position angle sometimes has sharp variations - Gonzalez + 2005 • Suggests ICL is dynamically young and separate from BCG PA (o) 50 0 -50 1 10 100 (kpc/h) 4 M. Arnaboldi – BCGs and ICL: observations ESO, FVC+, 27 June - 01 July 2011 ICL is ubiquitous – statistical properties • ICL has been found in – BCG dominated clusters (e.g., Gonzalez+’05) – in clusters without BCG (e.g., Feldmeier+’04, Struble88) • Average ICL+BCG and total (incl. galaxies) cluster surface brightness profiles, from stacking 683 (scaled) clusters from SDSS (Zibetti+’05): – ICL (=SB excess w.r.t. R1/4 profile of central BCG) is more centrally concentrated than cluster galaxies – <ICL fraction within 500 kpc> ~11%; BCG ~22% (**) – ICL SB correlated with BCG luminosity and cluster richness, but ICL fraction almost independent • ICL fraction in individual clusters varies: – ~4-21% (in B, Krick&Bernstein 2007) – ~10-30% (Feldmeier+’04) – ~5% in Virgo, isolated regions – ~50% in Bernstein+’95 field in Coma cluster core Depends on radial range and evolutionary stage of the cluster (**) robust values, measured from profiles M. Arnaboldi – BCGs and ICL: observations ESO, FVC+, 27 June - 01 July 2011 5 BCGs & ICL Dolag+2010 o Disentagle cD from ICL in clusters - use the velocity distribution of stars. o Simulations of clusters - VD is bimodal. Fit by two Maxwelliansdistribution, one narrower (colder) for the central galaxy and a broader one (hotter) for the ICL. o Hotter component is responsible for the “light excess” at large radii. o Stellar particles in hydrodynamical cosmological simulations thus selected turn out to have different spatial distribution & star formation history. See also Kapferer et al., 2010, MNRAS, 516, 41. Kinematics measurement can tag galaxy and ICL stars from their LOSVD at the same spatial location ! M. Arnaboldi – BCGs and ICL: observations ESO, FVC+, 27 June - 01 July 2011 6 2. Planetary nebulae as kinematical tracers • PNs trace light because the luminosity-specific stellar death rate should be independent of the precise state of the underlying stellar population (Renzini & Buzzoni 1986), see also PN.S results from Coccato+09. • PNs are distance indicators. • The [OIII] line emission at 5007Å is the strongest emission from a PN; it allows the identification & the measurement of its radial velocity ON-[OIII] ON-H OFF-(V+R) • We obtain PN number density distribution and 2D radial velocity fields in regions where the stellar surface brightness is too faint with respect to the night sky! M. Arnaboldi – BCGs and ICL: observations ESO, FVC+, 27 June - 01 July 2011 7 3. The core of the Virgo cluster Mihos et al. 2005, ApJ, 631, L41 & ESO PR 2009/19a -1 And this is where it all started: 3 PNs at vmean ~ 1400 kms along the LOS to -1 NGC 4406 (vsys = - 240 kms ) Arnaboldi, Freeman, et al. 1996, ApJ, 472, 145 M. Arnaboldi – BCGs and ICL: observations ESO, FVC+, 27 June - 01 July 2011 8 3. The core of the Virgo cluster Narrow band imaging plus spectroscopy ICPN catalogs from Arnaboldi+02&03, Feldmeier+03&04 6 VLT-Flames fields Core, FCJ, SUB from Arnaboldi+04 F7_1,F7_2, F4 from Doherty et al. 2009, A&A, 502, 771 52 PNs vlos total M87 halo according to Kormendy+09 photometry **For optical and Spitzer IRAC surface photometry in Virgo see also oral presentations of C. Rudick and J. Krick . M. Arnaboldi – BCGs and ICL: observations ESO, FVC+, 27 June - 01 July 2011 9 See also Freeman et al. 2000, ASP 197, 389, and Arnaboldi et al. 2003, AJ, 125, 514 for spectroscopic confirmation of ICPNs. M. Arnaboldi – BCGs and ICL: observations ESO, FVC+, 27 June - 01 July 2011 10 PNs’ LOSVD and projected phase space M87 halo • does not rotate. From GCs’ vrot -1 expects vave = 1150 kms for M87 halo PNs. M87 ICL •σ(r) decreases. From Montecarlo simulations of a Gaussian with σ=247 kms-1, the combined probability for 2 measurements at > -2σ and 5 within +/- 0.3 σ is less than 1%. ICL •No ICPN vLOS redder than 1800 kms-1 at R<3600”, while bluer velocities present at all radii. -1 •Broad velocity component at σPN = 247±52 kms @ 60 kpc -1 R>3600”. σPN = 78±25 kms @ 144 kpc M. Arnaboldi – BCGs and ICL: observations ESO, FVC+, 27 June - 01 July 2011 11 PNs’ LOSVD and projected phase space A04 ICPN detections Dwarfs spheroidals Red and blue symbols indicate the Doherty+09 PN detections. PNs with velocities higher than the mean velocity of the Virgo cluster (1100 km s−1) are shown as + ; those with lower velocities are shown as ○. The PNs associated with the peak at the M87 vsys are spatially segregated . There are no PNs at the M87 velocity at R > 150 kpc, while ICL PNs are scattered across the whole region! M. Arnaboldi – BCGs and ICL: observations ESO, FVC+, 27 June - 01 July 2011 12 Dynamical status of the Virgo core • The LOSVD of dEs+dS0s is flat and broad with a peak at M87 (1300 -1 kms ) with tails at vLOS<0 (Binggeli+87); asymmetry in the ICPN LOSVD in the Virgo core center. • Observed properties of the ICPN LOSVD are predicted in merging simulations of two sub-clusters with unequal mass along the LOS shortly before ~ 109 yrs the sub-clusters merge (Schindler & Böhringer 1999) . • Recent and on-going assembly of Virgo core: M87 falling backwards from the front and M86 forwards from the back (Binggeli+93). • The light in the M86 sub-group is tidally stripped by the more massive M87 component, while these two merge along the LOS - • We do not see a diffuse light with a broad velocity component redwards of M87 vsys because it has not yet been formed. M. Arnaboldi – BCGs and ICL: observations ESO, FVC+, 27 June - 01 July 2011 13 Large scale distribution of ICL in the Virgo cluster • RGB counts • PNs Arnaboldi+02,03,Aguerri+’05 • PNs Castro-Rodriguez+’09 PNs Feldmeier’04 M49 Radial Surface brightness from Virgo galaxies Bingelli+’87 ( - total, -.- giants, -…- dwarfs ) PN surveyed fields in the Virgo cluster (Castro-Rodriguez+09): PN number density is translated in B band. Surface Brightness (SB) and the large scale SB profile is plotted as function of the distance from M87 out to 4 degree = 1Mpc. M. Arnaboldi – BCGs and ICL: observations ESO, FVC+, 27 June - 01 July 2011 14 Large scale distribution of ICL in the Virgo cluster Surface number density maps for the globular clusters in comparison with the spatial distribution of galaxies and x-ray emission in the Virgo cluster region. DDEC and DRA are distances from M87 along declination and right ascension, respectively (Lee et al. 2010, Science 328, 334). M. Arnaboldi – BCGs and ICL: observations ESO, FVC+, 27 June - 01 July 2011 15 Large scale distribution of ICL in the Virgo cluster ICL distribution is clumpy & associated with the high density peaks in the Virgo cluster. There is not a smooth large scale light distribution out to the Virial radius of the Virgo cluster detected so far. ..A cautionary note for extrapolation of core ICL profile out to Virial radius for estimates of the baryonic fractions... M. Arnaboldi – BCGs and ICL: observations ESO, FVC+, 27 June - 01 July 2011 16 The next step beyond Virgo and Fornax …. The brightest PNe in the Coma cluster at 100 Mpc distance have fluxes of 2.2 10-18 erg/s/cm2 (~2 photons/min on 8m tel.). They cannot be detected using a narrow band filter because the noise in the 30 – 40 Å sky is of VLT + the same order of the signal we want to detect. FORS2 Subaru + FOCAS Ventimiglia et al. 2011, A&A, 528,24 Multi Slit Imaging Spectroscopy Technique (MSIS) Blind search: it combines a mask of parallel multiple slits with a narrow band filter, centred on redshifted [OIII] 5007 Å line at Coma mean systemic velocity, to obtain spectra of all PNe that lie behind the slits. The sky noise at the emission line of the PN come from few Å only, depending on slit width and spectral Gerhard et al. 2005, ApJ, 621, L93 resolution… M. Arnaboldi – BCGs and ICL: observations ESO, FVC+, 27 June - 01 July 2011 17 5.
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